This invention relates to a ball valve and more particularly to an improved metal seat design for a so-called floating ball valve.
Floating ball valves include a spherical ball valve member mounted within a valve chamber of the valve body for limited floating movement between upstream and downstream seats on opposed sides of the ball valve member. As compared with so-called trunnion mounted ball valves in which the spherical ball valve member is mounted on upper and lower trunnions for rotation and thus is fixed against any axial movement along the longitudinal axis of the flow passages, a floating ball valve moves in a direction along the longitudinal axis of the flow passages between opposed seats and is limited by such seats to a relatively small predetermined axial movement. As a result, when the ball valve member is in closed position and a high inlet fluid pressure exists, the ball valve member is moved against the downstream seat under a substantial force proportional to the inlet fluid pressure.
One of the problems associated with metal seat designs for floating ball valves is in the design of a seat which seals effectively at low fluid pressures, such as 5 psi, for example, and also seals effectively at high fluid pressures, such as 2000 psi, for example.
Heretofore, various types of metal seats have been provided for floating ball valves including metal seats which shift or rock into a sealing relation upon the application of a high fluid pressure against the ball member, with the seat recess being formed or shaped to accommodate or assist such movement. For example, U.S. Pat. No. 4,385,747 dated May 31, 1983 shows a metal seat mounted within a recess for facilitating movement of the seat under certain pressure conditions.
An example of another metal seat construction for a floating ball valve is shown in U.S. Pat. No. 4,557,461 dated Dec. 10, 1985 which has a metal seal of a substantial solid cross-section with a tapered and flexible lip extending therefrom for sealing against the ball valve member at low temperatures. While the lip is flexible, the remainder of the metal seal does not appear to be flexible to any significant degree.